This invention relates to a millimeter wave (MMW) radio frequency transceiver module using microwave monolithic integrated circuits.
Traditionally, millimeter wave (MMW) radio frequency modules have been assembled with xe2x80x9cchip and wirexe2x80x9d fabrication techniques, such as shown in FIGS. 1 and 2, where microwave monolithic integrated circuit (MMIC) chips 20 along with interconnecting substrates 22, such as made from alumina or fused silica, are bonded to a coefficient of thermal expansion (CTE) matched housing 24, which is normally formed from copper tungsten (CuW) or other similar CTE matched material. Metal plate capacitors 26 are mounted on the CTE matched housing 24 and have wire bonds 28 extending between the metal plate capacitors 26 and MMIC chips 20. Ribbon bonds 30 can extend between the MMIC chips 20 and any interconnections on the substrate 22. Various electrical interconnects 31 and other components can be printed on the substrates by techniques known to those skilled in the art.
FIG. 1 shows that the coefficient of thermal expansion matched housing 24 can have subminiature coaxial connectors (SMA connectors 32) and/or waveguide interfaces. The MMIC chips 20 and the substrates are typically adhered directly to the CTE matched housing by adhesive or other means. Various waveguide or other channels 34 are formed within the housing.
A drawback of this type of prior art xe2x80x9cchip and wirexe2x80x9d fabrication technique is its relatively expensive cost because of a high parts count and associated assembly costs. The present assignee has also made improvements by using multilayer, low temperature, co-fired ceramic (LTCC) board techniques, including the use of low transfer tape technology, where MMIC chips are mounted to multilayer LTCC boards. Multilayer board techniques reduce fabrication costs relative to the more traditional xe2x80x9cchip and wirexe2x80x9d fabrication techniques. There is still room, however, for other processing techniques that are improvements over xe2x80x9cchip and wirexe2x80x9d techniques besides the use of multilayer, low temperature, co-fired ceramic and low temperature transfer tape board techniques.
The present invention provides an improvement over prior art xe2x80x9cchip and wirexe2x80x9d fabrication techniques and comprises a millimeter wave (MMW) radio frequency transceiver module that includes a substrate board. A plurality of microwave monolithic integrated circuit (MMIC) chips are supported by the substrate board and arranged in a receiver section, a local oscillator section, and a transmitter section. A plurality of filters and radio frequency interconnects are formed on the substrate board and operative with and/or connect the receiver, local oscillator and transmitter sections. A plurality of electrical interconnects are operative with and/or connect the receiver, local oscillator and transmitter sections.
In one aspect of the present invention, the electrical interconnects are printed on the substrate board. In yet another aspect of the present invention, a dielectric layer and conductive layer are formed on the substrate board opposite to the side containing the MMIC chips, filters, and radio frequency interconnects. Electrical interconnects are formed within the conductive layer. A plurality of conductive vias extend from the electrical interconnects through the substrate board to the surface having the MMIC chips, filters and radio frequency interconnects.
In yet another aspect of the present invention, a cut-out can be formed within the substrate board for receiving a MMIC chip and allowing direct attachment of the MMIC chip to a coefficient of thermal expansion (CTE) matched carrier or heat sink. At least one row of ground vias are formed within the substrate board and provide isolation between at least the transmitter and receiver sections formed on the substrate board. The transmitter, receiver and local oscillator sections can be formed substantially isolated from each other to enhance isolation and reduce possible oscillations.
In yet another aspect of the present invention, a microstrip-to-waveguide transition is formed at each of the transmitter and receiver sections. Each microstrip-to-waveguide transition includes a backshort placed relative to the substrate board and a waveguide launch operative with the backshort. The backshort and waveguide launch are isolated by a plurality of isolation vias. The substrate board can comprise a single, ceramic board and can be formed from about 90% to about 99.6% alumina and ranges from about 5 to about 20 mil thick, in one aspect of the present invention.
In yet another aspect of the present invention, the transceiver module includes a housing made of aluminum or similar material having a bottom plate and a housing cover attached to the bottom plate. The substrate board is positioned on the bottom plate and covered by the housing cover. An electromagnetic interference gasket can be mounted within the housing cover such that when the housing cover is attached to the bottom plate, the interference gasket is positioned above the substrate and around MMIC chips supported by the substrate board. Radio frequency channels can be formed in the cover and an absorbent material is operative with the channels to enhance isolation among the local oscillator, transmitter and receiver sections. The housing cover includes solderless SMA connectors having spring-loaded intermediate contacts.
A method of forming a millimeter wave (MMW) radio frequency transceiver module is also set forth. A substrate board is formed and a plurality of microwave monolithic integrated circuit (MMIC) chips are mounted on the substrate board and arranged in a receiver section, a local oscillator section, and a transmitter section. A plurality of filters and radio frequency interconnects are formed on the substrate board, such as by thick film processing techniques, and are operative with and/or connect the receiver, local oscillator and transmitter sections. Electrical interconnects are formed and are operative with and/or connect the receiver, local oscillator and transmitter sections. In one aspect of the invention, a dielectric layer and conductive layer are formed on the substrate board opposite the MMIC chips and filters and radio frequency interconnects side. Electrical interconnects are formed within a conductive layer and a plurality of conductive vias are formed to extend from the electrical interconnects through the substrate board to the surface having the MMIC chips and thick film printed filters and radio frequency interconnects.